Wound transformers and machine for making the same

ABSTRACT

A wound transformer which can include additional capacitance and impedance members for its respective primary and secondary windings, and also an electrostatic shield. The transformer may be wound spirally, with a flat insulation winding holding interleaved metallic elements such as the primary and secondary winding, and a primary and secondary capacitance member. A primary and/or a secondary impedance member may be wrapped around all or part of a respective primary or secondary winding, in which event the winding material may have any desired crosssection. Means is provided expeditiously and economically to form the windings to a non-circular section.

United States Patent Kunkel Oct. 7,1975

[54] WOUND TRANSFORMERS AND MACHINE 3,378,626 4/1968 Tucker... 336/84FOR MAKING THE SAME 3,495,202 2/1970 Parker 336/223 3,634,800 1/1972Fisher..., 336/223 [76] lnventor: George M. Kunkel, 8402. 3,704,39011/1972 Grahame 336/69 McGroarty, Sunland, Calif. 91040 3,750,071 7/1973Elcy 336/84 [22] Filed: Dec. 11, 1972 Appl. No.: 313,847

Related U.S. App1icati0n Data Continuation-impart of Ser. No. 213,337,Dec. 29, 1971, abandoned.

US. Cl. 317/157.62; 336/192; 336/223 Primary ExaminerL. T. HiX Attorney,Agent, or FirmDonald D. Mon

[5 7] ABSTRACT spective primary or secondary winding, in which event thewinding material may have any desired crosssection. Means is providedexpeditiously and economically to form the windings to a non-circularsection.

54 Claims, 22 Drawing Figures illlllllllllll Sheet 1 of4 US. Patent Oct.7,1975

INVENTOR. GEO/QGf/W KU/VKfL b, M P

ATTORNEYS US. Patent Oct. 7,1975 Sheet 2 of4 L tr 5 mm w W. W a M W w 4Aa a m t B Z IA 0 3 n m 4 9 M K w n u u I J E v "m .m" z T 1 w m m a 9 lW :3 "u" 3 K 7 m u Z n OJ 1 6 n m M m \l in Cl F W F US. Patent 0m.7,1975

Sheet 4 of 4 WOUND TRANSFORMERS AND MACHINE FOR MAKING THE SAMECROSS-REFERENCE TO OTHER APPLICATIONS This patent application is acontinuation-in-part of applicants co-pending US. patent application,Ser. No. 213,337, filed Dec. 29, 1971, now abandoned.

This invention relates to a wound transformer which preferably has apolygonal cross-section, and to a method for winding the same. I

A transfonner is designed to transform a signal from a primary windingto a secondary winding where a specific frequency or a band offrequencies are of concern. By the nature of the design, frequenciesother than those of concern (known as noise) are also trans-' formed,and such transformation can be highly undesirable. It is known toattempt to minimize the noise transmission by utilizing an electrostaticshield, which is intended to reduce the effective capacitve couplingbetween one winding and another. Which a shield, as it has heretoforebeen constructed, has been very costly, and its reliability has beenrelatively low. Another known means for minimizing noise is to utilizelow-pass filters on the transformer leads. However, these are verycostly, add weight to the system, occupy excessive space, and canthemselves create a gain or loss at the desired transformer frequency,and can significantly affect the output voltage and power factor of thetransformer.

Transformers of the type contemplated by this invention may be expectedto be widely used in airborne arid space applications, and otherelectronic and commnication systems, and around computers where straysignals are intolerable. Although users are willing to spend whatevermoney it takes to reduce these undesirable features, the transformer ofthis invention accomplishes its objectives at a much lower cost intermsof weight, size and dollars than has heretofore been believed to bepossible.

Presently known transformers which utilize electrostatic shields havewindings formed of round wire which is wound upon a bobbin with flangeson both sides. When the transformer is wound in this manner and a simplefaraday shield is used, special insulation material must be utilizedbetween the inner winding and the shcild. Because the wires which leadto the inner winding must pass alongside the faraday sheild, the shieldmust be cut and then placed in such a fashion as to insure that theshield itself does not cut through the insulation of the wires. The leadwires which pass to the inner winding must also pass beside the outerwinding, thereby reducing the anticipated isolation which wouldotherwise be obtained by means of the shield, because of the resultantcapacitive coupling. Because the outer winding must be wound on top ofthe sheild, placing a low-impedance tab on the shield becomes difficultand awkward. Therefore, a wire is used, but the impedance of the wire inturn greatly reduces the effectiveness of the shield. Accordingly,attempts to utilize a faraday shield, which should be an elegantlysimple solution to at least a major part of the noise.

supplying'to the transformer an inductance and/0r impedance respectiveto the primary or secondary windings. Such means has not been attainablein the prior art, and this invention enables this objective to berealized. Such means significantly reduces noise, and doesso in acompact device which can readily and economically be manufactured.

ln adevice according to the invention:

A. a lesser transformer window area can be used in the design ofatransformerof 7 given properties;

B. the electrostatic shield may utilize the same material as thewindings of the transformer; I

.C. thesame material that insulates the windings fro each other can alsobe utilized to ins luate the electrostatic shield from the windings; I

(d). the breakdown voltage and capacitance between the transformerwindings and the electrostatic shield can be determined by selecting thenumber of turns of insulation material between them;

E. an extended electrostatic shield can be made from a single length ofmetallic material readily wound upon a bobbin;

F. external equipment can readily be connected directly to theelectrostatic shield and to the other metallic elements of the devicewithout reduction of reliability or increase in manufacturing .time andexpense;

G. the transformer can betwound on a square or a rectangular bobbinwhile maintaining the feed speed of the materials of contsruetion at arelatively constant velocity;

H. the internal direct leakagecapacitance of either the primary and/orthe secondary windings can be increased, resulting in restriction of thefrequency range at which the transformer will operate; and.

l. the internal leakage inductance-of either the primary and/or thesecondary winding can be increased, resulting in the restriction of thefrequency range at which the transformer will operate. 1

A transformerwinding member according to this invention is wound on abobbin. It comprises a spirallywound, continuous, wide piece ofelectrical insulation material, between the convolutions of which thereare placed spirally-wound turns of electrically conductive materialwhich are spaced apart from one another along the length of the spiralso as to'form'conductive portions of the transformer. There-may bewrapped between the turns of the insulation material a length ofelectrically conductive material similar to that of the windings whichstands between theprimary and secondary windings ,to -form anelectrostatic shield. The turns of insulation material which are formedbetween the turns of the windings and shield serve to insulate them fromone another and to form a transformer construction.

According to an optionalfeature, a plurality of layers of insulationmaterial may simultaneously be wound so that adjacent but electricallydisconnected conductive layers may be wrapped in adjacency 'to theprimary and secondary windings so as to form respective primary andsecondary capacitance members for reasons yet to be described. 1

According to still another optional feature of the invention.ferro-magnetic means may be inserted between certain turns of theinsultation member and then be wrapped around all or part of respectiveprimary pedarlce members, and as to this optional feature, the

impedance member may usefully be provided with windings of round wire,not merely with flat foil.

According to another preferred but optional feature of this invention,the winding member may be wound upon a square or rectangular bobbinutilizing a belt drive driven at a constant linear velocity, which beltwill drive the bobbin at an oscillating angular rate which, however,draws the material of construction 'from a source of supply at aconstant rate that is directly proportional to the velocity of the belt.

The above and other features of this invention will be fully understoodfrom the following detailed description and the accompanying drawings inwhich:

FIG. I is a classical T drawing of the equivalent circuit for atransformer;

FIG. 2 is a T drawing showing the equivalent circuit which results ifthe transformer is modified by the addition of an electrostatic shieldbetween the primary and secondary windings;

FIG. 3 is a T" drawing showing the equivalent circuit which results ifthe transformer is modified by the further addition of a primary and asecondary capacitance member and a primary and a secondary inductancemember;

FIG. 4 is a schematic drawing showing the construction of one embodimentof a transformer winding member according to the invention;

FIG. 5 is a cross-section of part of one turn in FIG.

FIG. 6 is an end view of a completed winding member according to theinvention;

FIG. 7 is a cross-section taken at line 77 of FIG. 6;

FIG. 8 is a side view'showing a feature of construction of the inventionin an intermediate stage of manufacture;

FIG. 9 is a view the same as FIG. 8, but with the constructioncompleted;

FIG. 10 shows the winding member of FIG. 6, to gether with a magneticcore which completes the transformer;

FIG. 11 shows an alternate embodiment of the invention;

FIG. 12 is a side view, partly in cutaway crosssection, schematicallyshowing a device for winding the winding member of FIG. 4;

FIG. 13 is a cross-section taken at line l3l3 of FIG. 12;

FIG. 14 shows the winding member of FIG. 4 in the process of itsmanufacture, utilizing a preferred embodiment of the device of FIG. I2;

FIG. 15 is a side view, partly in cutaway crosssection, showing thewinding device of FIG. 12 in further detail;

FIGS. 16 and 17 are fragmentary laid-out views schematically showingsome considerations regarding the electrostatic shield; I

F IG. [8 is a fragmentary cross-section of a modified part of FIG. 4;

FIG. 19 is a fragmentary laid-out view taken at line 19l9 of FIG. 18;

FIG. 20 is a fragmentary view of a modified portion of FIG. 6;

FIG. 21 is a fragmentary cross-section taken at line 2l-2l of FIG. 20;and

FIG. 22 shows a modification of a portion of FIG. 9.

Some of the features of this invention can be utilized in transformersof conventional design, and with theuse of wound wire. However, whenfiat foils are used for the conductive elements of the transformer, allof the features can be used, and there results a tranformer whichconstitutes a major stride in the art.

A conventional transformer basically consists of an iron core with apair of windings around it which are inductively linked to each other byit. One of the problems inherent inconventional transformers is thetransmission of noise between windings derived from undesirableelectrostatic and electromagnetic effects. For this reason, andelectrostatic shield and external filters are often provided. Anelectrostatic shield is a grounded conductive shield that stands betweenthe two windings, and this does tend to reduce the noise.

It is not generally realized that further improvements can result fromthe provision of a capacitive property within each of the primary andsecondary windings, and from the provision of an inductive propertywithin each of them. Previous to this invention, such realization wouldhave done little good, because there was no means to provide the same ina practical and economical transformer. This invention makes such atransformer practical. It eliminates the need for bulky and costlyin-Line filters.

It is not considered necessary or even appropriate in this specificationto develop the underlying theory of behavior of the transformer itself.Suffice it to say that, with the construction disclosed herein,transformers can readily be manufactured which have the equivalentcircuits shown in FIGS. 2 and 3, and which, when their physicalproperties are selected appropriately with respect to the circuit inwhich they are to be used, produce an output which is as free of noiseas is attained by the best of the presently known transformer-filtersystems. 1

In FIGS. 1, 2 and 3, the symbols have the following meanings:

R,, Primary Resistance R Secondary Resistance R Shunt Core-LossResistance" 7 k L Primary Shunt (mutual) Inductance C,, PrimaryDistributed Capacitance C Secondary Distributed Capacitance L PrimaryLeakage Inductance L Secondary Leakage Inductance C DirectInput-to-Output Leakage Capacitance C Direct Primary Leakage CapacitanceC Direct Secondary Leakage Capacitance As to the effects of the variouselements, the following statements apply: I

The addition of:

A. Primary inductance increases 1.

B. Secondary inductance increases L I C. Primary capacitance increase CD. Secondary capacitance increases C and E. Electrostatic shielddecreases the effective leakage capacitance C Persons skilled in the artwill recongize from FIGS. 1-3 and the above statements theutility of thevarious elements, the means for selecting their parameters for bestresults, and the means for connecting them into appropriate circuitry.

An object of this invention is to provide means not only for winding alightweight, inexpensive and efficient transformer which need not havean electrostatic shield, but also one which may not only have aneffective electrostatic shield but one which may also, or instead, haveadditional primary and secondary capacitance and impedance membersassociated with the respective windings. Furthermore, this inventionaccomplishes these objectives by means which can be manufactured at ahigh rate of production.

Because of the use of the impedance members, and for the most effectiveuse of a magnetic core yet to be described, it is preferable to wind thewinding member of the transformer on a noncircular, polygonal bobbinwhich is rectangular. Many of the objectives of this invention can beachieved with a round bobbin, but in that case, the impedence memberscannot ordinarily be as conveniently provided.

The presently preferred embodiment of winding member 35 for theinvention is shown in FIG. 6. It includes a mounting member 36, which isa hollow prismatic structure made of insulating material, upon whichthere is spirally-wound a primary section 37, a separation section 38and a secondary section 39. These sections will be more fully discussedin detail later in this specification.

A primary impedance member 40 and a secondary impedance member 41 arewrapped around all or part of the respective primary and secondarysections in a manner yet to be described.

Primary leads 42, 43, secondary leads 44, 45, electrostatic shield lead46, primary capacitance lead 47, and secondary capacitance lead 48extend from internal portions yet to be described, and are for thepurpose of connecting the appropriate parts of the transformer toexternal cicuitry.

The winding itself is formed by spirally winding around a bobbin, whichfor this purpose may be considered the mounting member 36, a layer 50 ofinsulation material such as mylar or teflon. Other materials which havegood insulating properties and sufficient flexibility, such as paper,may instead be utilized. It ispreferably fed from a reel and is bestshown in FIG. 7 as having a dimension 5] of width and a dimension 52 oflength. It is wound on the bobbin so as to form a winding with a centrallongitudinal axis 53 (FIG. to which the dimension 51 of width isparallel. The spiral will wind to form a stack of increasing thicknessas the bobbin is turned so as to form the successive turns orconvolutions.

Similarly, an elelectrically conductive material is utilized to form thevarious windings, shields and other members. It is best shown in FIG. 8.This material is laid down in the form of layers 54 having a dimension55 of width, which will generally be less than the dimension of width ofthe insulation material, and a dimension of length parallel to that ofdimension 52. The conductive material is preferably selected from thegroup consisting of aluminum, aluminum alloys, copper and copper alloys,although any conductive material of suitable electrical properties mayinstead be used.

In the construction of this device, and depending upon the voltages tobe transformed and the loads which are to be carried by it, thethickness of the layers of insulating and metallic material are those offoils, and they conveniently have a minimum width and thickness asdictated by the said voltage and current.

It is evident that the insulation material will be formed as acontinuous length and will comprise the fundametnal building unit of thewinding member. The electrically conductive material will be fedintermittently for just so many turns as are required to construct therespective element and then, for electrical spacing between the two,metallic material will not again be fed until a sufficient number ofturns of insulation material have been wrapped to give the desiredamount of spatial and electrical separation from the other conductiveelements. Accordingly, this device, when made in its simplest manner,comprises a continuous spiral turn of insulation material interleavedwith a primary winding and a secondary winding between adjacentinsulation convolutions, and spaced apart from one another electricallyby a plurality of turns of insulation material which do not haveadjacent to them any of the electrically conductive material. Similarly,the electrostatic shield is formed by providing a length of theelectrically conductive material in the separation section where it isboth spatially and electrically disconnected from the primary andsecondary windings. As will later be discussed, it is preferable forthis length to be such as to form one complete turn, but the provisionof less than one complete turn is also contemplated by the invention. Inthese two forms of the invention, where there are no immediatelyadjacent turns of electrically conductive material, with or withoutelectrostatic shield, it is only necessary to utilize one layer ofinsulation material because, when it returns around the next turn, itwill overlay any adjacent metal material. If, however, thereare to betwo concurrent metallic turns such that one metal layer will overlap theother within the same turn, then there must be two or more layers ofinsulation material utilized, and it is this feature which enables thecapacitance members to be formed in the manner yet to bedescribed.Accordingly, this most complicated means of manufacture of the devicewill be described herein, it being understood that the simpler forms ofthe transformer, namely one without an electrostaic shield, or with anelectrostatic shield but lacking the capacitance windings, can be madeutilizing only one single layer of insulation material, and only a partof the windingma'chine, where the primary and secondary windings and theelectrostatic shield can be of different pieces frorhfthe same roll ofmaterial.

The winding member of FIG. 6, which is schematically shown in FIG. 4, isconstructed by means of the machine shown in FIG. 15. The machine 60 hasa shaft 61 turning a bobbin 6iwhich has a square periphery 63. Themounting member 36 is mounted onto the square periphery, and the windingmember is formed by rotating the bobbin in the direction indicated byarrow 64.

Reels 65, 66 carry lengths of insulation material, while reels 67, 68carry metallic materials. The outfeed from the reels is intended to beat a substantially constant linear velocity, and the material passesfrom the respective reels over idler wheels 69, which are appropriatelyplaced so as to gather and guide the materials. The supply of theinsulation material will be continuous, but that of the metal will bediscontinuous. Flying knives or other intermittent cutting and feedingdevices, the details of which form no part of this invention, will beprovided for the discontinuous insertion of lengths of metal materialbetween the layers of insulation at the appropriate times.

Because the bobbin is non-circular, and because it is desirable to haveas constant a velocity of feed of the foil material to the bobbin aspossible in order to avoid wrinkling and breakage, the machine isconstructed so as to exert a steady demand. As best shown in FIG. 12,

a drive wheel 70 is provided which drives a belt 71 at a constant linearvelocity. this belt engages a shaft 72 which has an outer driveperiphery 73 that is gemetrically similar to, and preferably of aboutthesame dimensions as, those of the mounting member 36. Accordingly, theangular velocity of the central shaft 72 will fluctuate periodically asthe belt drives at a constant linear velocity.

A web 74 of material, which'may be considered the output from the reelsshown in FIG. 15, is wrapped around the similarly shaped mountingmember. The result of driving a square bobbin by a continuously movingbelt, and then winding the web material onto a surface of geometricallysimilar shape, results in motion of the web of a linear velocity whichis constant within the tolerances which can be withstood by thematerial. Of course, if a square bobbin is not used, then the shape ofthe drive shaft will be similar to whatever shaped is used, instead ofbeing square. I

This mechanism comprises a very simple means for forming a non-circularwinding without having'to vary the speed of supply at the source. Itwill be recongized that, as the winding grows on the bobbin, thesimplified geometrical relationship show in FIG. 12 will changesomewhat, and a means of overcoming this disadvantage is shown in FIG.14.

In FIG. 14, drive wheel 70 is shown'in three successive positions, 75,76 and 77, which positions result from being moved along a track as thewinding grows on the bobbin. This movement need not be particularlylarge, and it has as its objective to maintainthe web portions 78sensibly parallel to, or perpendicular to, the drive belt portions 79.The angular relationships will be the same when the drive belt isperpendiculr as when it is parallel, and both arrangements arecontemplated by this invention. As a result, the velocities of the beltand of the web will remain substantially constant and directlyproportional to one another. A simple means to accomplish this objectiveis'to shift the center of the wheel along an arc defined by positions75, 76 and 77, using a lead screw which' responds to the number of turnsplaced on the bobbin; The drive wheel 70 is reset to its initialposition 75 each time that a new winding is to be wound.

The reason for'the periodic variation in-the shaft speed, theunfortunate aspects of which are overcome in this arrangement, isillustrated by the two bobbin positions 80, 81, which are shown in solidand coded line, respectively. These illustrate that, unless anarrangement is made such that the angular velocity of the bobbin varies,there would be a variationin the instantaneous velocity of the web awayfrom its source. This is overcome by the simple expediant of driving ashaft at a surface which has an external configuration which isgeometrically similar to that of the surface upon which the winding isbeing wound, so that the demand is the sameas the drive, i.e., constant.

With the foregoing in mind, reference should now be made to FIG. 4,wherein only the electrically conductive portions of the winding memberare shown. An attempt also to-incorporatein this drawing the insulationlayers results in an overly-large and dazzling drawing which is mostdifficult to read, I

Primary winding 85 is shown in solid line as having three completeturns. A complete turn is defined as a continuous length of materialwhich, when wound around the axis, will intersect a single radius twice.An

electrostatic shield 86, shown in dashed line, is radially spaced apartand electrically spaced from winding 85. It has overlapped ends andpreferably forms slightly more than one complete turn so as completelyto shield the primary winding. I-Iowever,as will later be discussed,this invention comprehends the usage of an electrostatic shield of lessthan and more than one complete turn, and whose width compared to thatof the windings is equal to, or greater, or less than they are. Outside,and wrapped around the electrostatic shield, is secondary winding87,also shown in solid line and having three turns, this being shown forconvenience as a 1:1 transformer, although the ratio could, of course,be otherwise. Without the electrostatic shield, the primary andsecondary windings would comprise a classical simple transformer. Withthe electrostatic shield, it comprises an improved transformer. Eitherof these constructions could be made by utilizing only a single wrapping(length) of insulation material in the sense of being made from a singlepiece. During the turns where the primary winding exists, the lastprimary turn will be covered by the next turn of the insulation. Then afew wrappings of insulation will be made to give the desired isolationfor the electrostatic sheild. Next, the electrostatic shield will be fedfor one full turn, or whatever greater or lesser amount is to beprovided, after which additional turns of insulation material withoutconductor adjacent thereto will be fed. This is followed by therequisite number of turns for the secondary windings, and wrapping willcontinue until the desired number'of turns is formed. Thereafter, theexternal insulation is wrapped in place.

The winding member shown in FIG. 4 includes not only thealready-described primary and secondary windings and electrostaticshield, but also a primary capacitance member 88 and a secondarycapacitance member 89 which are shown in coded line. As can be seen inFIG. 4, the primary capacitance member occupies one complete turn, asdoes the secondary capacitance member. This invention comprehends theusage of capacitance members of less than, and more than, one completeturn, and whose width compared to that of the windings is equal to, lessthan, or greater than, they are. Because these capacitance members areinserted between convolutions of their respective primary and secondarywindings, there must be used an additional layer of insulation materialin order to receive and insulate the capacitance members from theirrespective primary or secondary winding. Of course, this additionalinsulation layer may intermittently be supplied in the same manner asthe metal members, should it be desired not to use as much insulationmaterial throughout, but usually it will form a continuous spiralthroughout the entire winding member.

The insulation layers are shown as extending throughout, there being twoof them, and indicated by arabic numerals 1 and 2. As can best be seenin connection with the primary winding and the primary capacitancemember, insulation layer 1 lays next to the mounting member 36, theprimary winding lays between it and layer 2, and layer 2 is overlaid bythe pri- .mary-c apacitance member, which, on the completion members,meaning that it may be drawn'from either one of reels 67 or 68. It willnow be seen that the windings, the electrostatic shield and thecapacitance members may be wound together so as to be axially alignedand form the complete contruction of the winding element.

Should the additional primary and secondary impedance members bedesired, then at an appropriate time the winding operation will bestopped and a plurality-of flexible metal, preferably soft iron plates,90 will be laid along the bobbin with their axis of length parallel toits central axis. These plates are best shown in FIG. 7 whichillustrates the secondary impedance member. The plates are wrappedaround the secondary section 39, and their ends 91 are interleaved.Their free ends may be held down adhesively or by fastener means.Similarly, the primary section will have been laid down against thebobbin before the winding began, and then the winding.will bediscontinued for a monent when the primary section is completed, itsrespective metal leaves similarly assembled, and then the separationsection will be formed around it. The illustrated winding deviceprovides a convenient means for making such a construction.

There are, of course, means which can provide the inductance membersother than interleaved layers. Rings or other structures which embracethe respective primary or secondary winding are also suitable, so longas they are made of magnetizable material.

Similarly, the utility of the inductance members is not restricted touse with flat foils. This feature can also be used with windings formedfrom materials of other cross-sections, such as from round wire. Whilethe capacitance members can only be used within flat spirals, the sameis not true of the inductance members, which can be used with windingsmade of materials of any desired cross-section.

FIGS. and 21 illustrate further considerations pertinent to theimpedance member. (Throughout the specification and claims, the termsimpedance member and impedance means are used interchangeably withinductance member and inductance means). Primary section 37, separationsection 38, and secondary section 39 are shown. In FIG. 6, impedancemembers 40 and 41 embrace all of the turns of their respective sections.In FIG. 21, a secondary impedance member 130 is shown embracing onlypart of the turns of the secondary-section 39. This same arrangement canbe used for the primary impedance member, and, of course, in anyembodiment, only one or the other of the impedance elements can be used,instead of both.

Also, the term embrace, as used to define the structural relationshipbetween the impedance member and the turns it embraces, does notnecessarily mean total encirclement, although it can, and in FIG. 7 itdoes. In FIG. 21, the ends 131, 132 form a gap 133 be tween them. Thus,the inductance or impedance of the impedance means can readily beselected as a function of the properties of its material, and by whethera gap is provided, and if so, its size. FIG. 21 also illustrates thatthe impedance member can be formed by a single plate of magnetizablematerial such as iron, instead of by a stack. Its ends could beoverlapped if desired, as in FIG. 7, instead of forming a gap as shown.Similarly, the stack in FIG. 7 could terminate at a gap (zero orappreciable spacing) instead of an overlapped structure.

As heretofore stated, the attachement of leads to the various sectionsof conventional transformers has been very troublesome. Thisdisadvantage has been completely overcome in the instant invention bymeans shown in FIG. Sin which an end 92 of such metallic portion as isbeing constructed is folded to a 90 bend so as to project laterallysideward of the underlying material, and then is given additional folds92 (FIG. 9) to form a strong, rugged tab integrally connected withoutdiscontinuity to the respective metallic element. The additional foldscreate at least one dorsal fold 93a and a monolithic self-reinforcingstructure results wherein all layers of the folds are mutuallyinterconnected and mutually reinforcing. It is this folded end which isshown as the leads 42-48 in every case.

The folded tabs shown in FIGS. 8 and 9 constritute a most convenient andreliable form of connection to the foil element. There are, of course,other means of connection, for example, by attachment to the foils ofconductive adhesive tapes, of clips, soldered bonds or cold-weldedjoints. Any suitable connector may be used with transformers accordingto this invention.

FIG. 22 illustrates an elegantly simple means to attach the tabs toother structure. It is simplyan aperture 135 formed continuously throughall of the contiguous folded layers. Obviously, thisis a punched hole,

punched after the tab is made. All of the layers serve to reinforce oneanother, and the construction is surprisingly resistant to tearing outat the hole. By being folded in the manner illustrated, no notches areformed in the foil which could tend to encourage tearing, and the tab isinsulated by the adjacent layers of insulating material, except for theportion which extends axially beyond the winding.

The transfonner construction is completed by means of an iron core 96(FIG. 10), which may be a typical C core construction having twoC-sections 97 and 97a. The core passes through the central portion ofthe winding member. There results a transformer which can readily bewound of simple, lightweight material of minimum envelope dimensionswhich can have as few or as many turns as desired, which can effectivelybe shielded, whose electrical members can be connected by integralmeans, and which can be provided with impedance and/or capacitancemeans, and with an electrostatic shield. The materials of constructionare inexpensive, and, by the use of the mechanism shown in FIGS. 12-15,the cost of manufacturing the transformer is kept to a minimum. 7

The preferred embodiment of this invention involves the winding of allelements into a single roll. This consturction involves fewest parts.However, it is also possible to secure the advantages of this inventionin a device which utilizes two winding members, as shown in FIG. 11. Inthis device, primary winding member and secondary winding member 11 areassembled on a core 112 made of two C shaped halves. Each winding isspirally wound with a respective primary or secondary winding as before,but each has only a primary or a secondary winding. If an electrostaticshield is used, it is formed as a convolution wrapped around therespective winding, so as to shield the winding from electrostaticeffects of the other winding. A shield may be placed on only one, or onboth, of the windings.

Similarly the capacitance members can be wound into the respectiveseparate Winding member, and also a respective inductance member (notshown) can be wrapped around the same. The import of FIG. 11 is that theadvantages of the invention can be secured with the use of more than onewinding member.

When the transformer is connected into the illustrated circuit, itsprimary and secondary winding terminals are connected in the usualmanner. The terminal of the electrostatic shield is connected to ground,and the terminals of the capacitance members are connected to respectiveones of the terminals of the primary and secondary windings. For othercircuits, different connections could be made, for example, thecapacitor elements could be connected to ground, and the electrostaticshield to one of the primary or secondary windings. This transformer isa device of broad application, and there are many ways of connecting itselements to other circuitry and to themselves in addition to thearrangement shown in the drawings, which arrangement'i s given by way ofillustrating one usage, and not as a limitation on the scope of theinvention.

The bulk of the transformer, while about the same as that ofconventional transformers, results in a substantial reduction in systembulk and weight, because its performance enables peripheral equipment,such as filters and the like, to be eliminated.

One suitable 125 watt transformer according to the invention utilizes295 turns in the primary winding, 306 turns in the secondary winding, 1turn in the electrostatic shield, and 37 turns in each of thecapacitance members. It utilizes a stack of thin soft iron plates foreach inductance member, the plates being about 0.004 inch thick, withtheir ends abutted against each other, this being a "zero or minimalgap, but a gap nonetheless. The foil is about 3 inches wide and 0.0005inch thick. The insulation material is mylar, about 3% inches wide and0.0002 inch thick. About 200 turns of insulating material isolate theprimary winding from the secondary winding.

The terms foil and flat" have been used herein to denote a materialwhich, in the transformer winding element, will be wound turn on turndirectly one upon the other. In the usual case, but not in every case,this will dictate the use of relatively thin material of significantwidth, for example, a thickness less than about 0.050 inch, and a widthusually at least about an inch. However, dimensions outside this rangemay also be used, but without some of the advantages that are inherentwithin this range.

It is pertinent to notice that, as to the capacitance members 88 and 89,they form one plate of a capacitor, the other plate being the respectiveprimary or secondary winding. Appropriate circuit connections will bemade to secure the advantages of this capacitance.

In the case of both the capacitance members and impedance members, thesize and extent of the areas confronting the respective windings are thepertinent consideration. FIGS. 16 and 17 illustrate, laid out, one fullturn of primary winding 85, and less than one full turn of electrostaticshield 86, whose width is respectively less than and greater than thatof the winding material. Arrows 140, 141, 142 indicate the windingdirection. In the preferred embodiment, the electrostatic shield extendsfor at least one full turn, and has a width as great as that of thewinding. Then full shielding results, and this could perhaps be improvedby making the shield material wider (FIG. 17), although this addscomplexity to the manufacture of the winding.

However, substantial electrostatic shielding can be secured with lessthan full area occlusion by the shield. In fact, a reduction of 20db ofnoise will be achieved in many transformers with a shield whose lengthis only of a full turn (or a full turn with a shield of 75% width). Theimport of this is that one can secure many of the benefits of thisinvention by only partial shielding, and this is within the scope of theinvention.

FIG. 17 shows a shield which is shorter than one turn, and which has awidth greater than that of the winding.

The reference to primary or secondary winding in FIGS. 16-21 isapplicable to either, those specifically referred to being given only asexamples.

FIGS. 18 and 19 shown primary winding and primary capacitance member 88,wound in the insulation member. FIG. 19 shows a laid-out full turn ofthe primary winding 85, and a primary capacitance member 88 whose lengthand width are less than those of the turn of the primary winding. Thus,the area of the capacitance member is less than that of the full turn ofthe primary winding, and, of course, the capacitance is a function ofopposed areas. The length of the capacitance member could be greaterthan one turn, less than one turn, and the width equal to, or greater,or less than that of the winding, the value of all of these variablesbeing selectible to establish the capacitance at a de sired level. Thus,there is no special upper or lower limit on the legth or width of thecapacitance members,

other than that it should face an area of its respective winding andprovide the proper capacitance.

To summarize, capacitance members and impedance members can be used witheither or with both of the primary windings, the area of theelectrostatic shield and the capacitance members may be adjusted toachieve a desired effect, and the impedance member may be used with orwithout overlapping the plate 'or plates, and with an abutment type gapor significantly sized air gap, and embracing all or only part of theturns of the respective winding. 7 i

This invention is not to be limited by the embodiments shown in thedrawings and described in the description, which are given by way ofillustration and not of limitation, but only in accordance with thescope of the appended claims. j

I claim:

1. A transformer winding member having a central axis, comprising; aspirally-wound layer of flat insulation material forming a spiral andhaving a dimension of length which is wrapped around the axis, and adimension of width which extends in the said axial direction, therebeing a plurality of turns of said material; a primary winding and asecondary winding of flat electrically conductive material having adimension of length which is wound around the axis, and a dimension ofwidth which extends in the said axial direction which is no greater thanthe dimension of width of the insulation material, each of said windingscomprising at least one full turn; an electrostatic shield of flatelectrically conductive material having a dimension of length which iswound around the axis, and a dimension of width which extends in thesaid axial direction, said windings and shield lying between turns ofsaid insulation material, and being radially spaced from one another byturns of the insulation material, and separated from one another alongtheir dimensions of length, the shield lying between the windings andbeing axially aligned with at least a portion thereof.

2. A transformer winding member according to claim 1 in which terminalmeans for said windings and shield comprises and end portion of thematerial of the respective winding or shield folded to project laterallybeyond the winding member, the projecting portion being multiply folded,whereby to form a plurality of dorsal folds extending longitudinallyalong the projecting portion to form the said portion as a monolithicstructure.

3. A transformer winding member according to claim 1 in which theprimary and secondary windings and their contiguous insulation materialrespectively comprise a primary and secondary section, theinsulationmaterial between these sections comprises a separation section, therebeing an impedance means of magnetizable material embracing in a radialplane at least a portion of one of the respective primary and secondarysections.

4. A transformer winding member according to claim 3 in which the saidimpedance means comprises a metal plate.

5. A transformer winding member according to claim 3 in which saidimpedance means comprises a plurality of iron plates in a stack, withtheir ends interleaved.

6. A transformer winding member according to claim 1 in which acapacitance member of flat electrically conductive material is wrappedinto the spiral within a winding, being separated therefrom by saidinsulation means on both of its sides, and being electrically insulatedfrom all other metallic elements of the winding member.

7. A transformer winding member according to claim 6 in which acapacitance member is wrapped into both the primary and secondarywindings.

8. A transformer winding member according to claim 6 in which theprimary and secondary windings and their contiguous insulation materialrespectively comprise a primary and secondary section, the insulationmaterial between these sections comprises a separation section, therebeing an impedance means of magnetizable material embracing in a radialplane at least a portion of one of the respective primary and secondarysections.

9. A transformer winding member according to claim 8 in which the saidimpedance means comprises a metal plate.

10. A transformer winding member according to claim 7 in which theprimary and secondary windings and their contiguous insulation materialrespectively comprise a primary and secondary section, the insulationmaterial between these sections comprises a separation section, therebeing an impedance means of magnetizable material embracing in aradialplane at least a portion of only a respective one of therespective primary and secondary sections.

11. A transformer winding member according to claim 10 in which the saidimpedance means comprises a metal plate.

12. A transformer winding member according to claim 10 in which saidimpedance means comprises a plurality of iron plates in a stack, withtheir ends interleaved.

13. A transformer winding member according to claim 6 in which terminalmeans for said windings and shield comprises and end portion of thematerial of the respective winding or shield folded to project laterallybeyond the winding member, the projecting portion being multiply folded,whereby to form a plurality of dorsal folds extending longitudinallyalong the projecting portion to form a monolithic structure.

14. A transformer winding member according to claim 7 in which terminalmeans for said windings and shield comprises an end portion of thematerial of the respective winding or shield folded to project laterallybeyond the winding member, the projecting portion being multiply folded,whereby to form a plurality of dorsal folds extending longitudinallyalong the projecting portion to form a monolitic structure.

15. A transformer winding member according to claim 10 in which terminalmeans for said windings and shield comprises an end portion of thematerial of the respective winding or shield folded to project laterallybeyond the winding member, the projecting portion being multiply folded,whereby to form a plurality of dorsal folds extending longitudinallyalong the projecting portion to form a monolitic structure.

16. In combination: a transformer winding member according to claim 1,and a magnetic core member encircling the same and passing through thecenter thereof.

17. A combination according to claim 16 in which terminal means for saidwindings and shield comprises an end portion of the material of therespective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form a monolithic structure.

18. A combination according to claim 16 in which the primary andsecondary windings and their contiguous insulation material respectivelycomprise a primary and secondary section, the insulation materialbetween these sections comprises a separation section, there being animpedance means of magnetizable material embracing in a radial plane atleast a portion of one of the respective primary and secondary sections.

19. A combination according to claim 16 in which a capacitance member offlat electrically conductive material is wrapped into the "spiral withina winding, being separated therefrom by said insulation means on both ofits sides, and being electfiically insulated from all other metallicelements of the winding member.

20. A combination according to claim 19 in which the primary andsecondary windings and their contigu-- ous insulation materialrespectively comprise a primary and secondary section, the insulationmaterial between these sections comprises, a separation section, therebeing an impedance means of magnetizable material embracing in a radialplane at least a portion of one of the respective primary and secondarysections.

21. A transformer winding member according to claim 1 in which theelectrostatic shield extends for at least one full turn, and is at leastas wide as the primary and secondary windings.

22. A transfonner winding member according to claim 6 in which thecapacitance member extends for at least one full turn.

23. A transformer winding member according to claim 22 in which theelectrostatic shield extends for at least one full turn, and is at leastas wide as the primary and secondary windings.

24. A transformer winding member having a central axis, comprising: aspirally-wound layer of flat insulation material forming a spiral andhaving a dimension of length which is wrapped around the axis, and adimension of width which extends in the said axial direction, therebeing a plurality of turns of said material; a winding of flatelectrically conductive material having a dimension of length which iswound around theaxis, and a dimension of width which extends in the saidaxial direction which is no greater than the dimension of width of theinsulation material, said winding comprising at least one full turn; andelectrostatic shield of flat electrically conductive material havinga'dimension of length which is wound around the axis, and a dimension ofwidth which extends in the said axial direction, said winding and shieldlying between turns of said insulation material, and being radiallyspaced from one another by turns of the insulation material, andseparated fron one another along their dimensions of length, the shieldlying outside the winding and being axially aligned with at least aportion thereof.

25. A transformer winding member according to claim 24 in which thewidth of theelectrostatic shield is at least as great as the width ofthe winding.

26. A'transformer winding member according to claim 24 in which terminalmeans for said winding and for said shield comprises an end portion ofthe material of the respective winding or shield folded to projectlaterally beyond the'winding member, the projecting portion beingmultiply folded, whereby to form a plurality of dorsal folds extendinglongitudinally along the projecting portion to form a monolilthicstructure.

27. A transformer winding member according to claim 24 in whichimpedance means of magnetizable material embraces in a radial plane atleast a portion of the winding. I

28. A transformer winding member according to claim 27 in which the'saidimpedance means comprises a metal plate. i

29. A transformer winding member according to claim 27 in which saidimpedance means comprises a plurality of iron plates'in a stack, withtheir ends interleaved.-

30. A transformer winding member according to claim 27 inwhich'saidimpedaneemeans comprises a metal plate *whose'ends arespacedapart by a gap.

31. A transformer-winding member according to claim 24 in which acapacitance member of flat electrically conductive material is wrappedinto the spiral within the winding, being separated therefrom by saidinsulation means on both of its sides, and being electrically insulatedfrom all other metallic elements of the winding member.

32. A transformer winding member according to claim 31 in whichimpedance means of magnetizable material embraces in a radial plane atleast a portion of the winding.

'33. In combination: a pair of transformer winding members according toclaim 24, and a magnetizable metallic core member extending through acentral axial opening in both of said transformer winding members.

34. A combination according to claim 33 in which terminal means for saidwinding and for said shield comprises an end portion of the material ofthe respective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form a monolithic structure. 7

35. A combination according to claim 33 in which impedance means ofmagnetizable material embraces 16 in a radial plane at leastaportion ofone of said winding sections. Y

36. A combination according to claim 33 in which a capacitance memberof-flat electrically conductive material is wrapped into the spiral ofat least one of the winding members, and being separated therefrom bysaid insulation material on both of its sides, and being electricallyinsulated from all other metallic elements of the winding member.

37. A combination according to claim 36 in which impedance means ofmagnetizable material embraces in a radial plane at least a portion ofone of said winding sections.

38. A transformer winding member having a central axis, comprising: aspirally-wound layer of flat insulation material forming a spiral andhaving a dimension of length which is wrapped around the axis, and adimension of width which extends in the said axial direction, therebeing a plurality of turns of said material; a primary winding and asecondary winding of flat electrically conductive material having adimension of length which is wound around the axis, and a dimension ofwidth which extends in the said axial direction which is no greater thanthe dimension of width of the insulation material, each of said windingscomprising at least one full turn; said windings lying between turns ofsaid insulation material, and being radially spaced from one another byturns of the insulation material and separated from one another alongtheir dimensions of length; and an impedance means of magnetizablematerial embracing at least a portion of only a respective one of thewindings in a radial plane. I

39. A transformer winding member according to claim 38 in which the saidimpedance means comprises a metal plate.

40. A transformer winding member according to claim 39 in which a gap isformed between the ends of the plate. I i

41. A transformer winding member according to claim'38 in which saidimpedance means comprises a plurality of iron plates in a stack, withtheir ends interleaved.

42. A transformer winding member having a central axis, comprising: aspirally-wound layer of flat insulation material forming a spiral andhaving a dimension of length which is wrapped around the axis, and adimension of width which extends in the said axial direction, therebeing a plurality of turns of said material; a primary winding and asecondary winding of flat electrically conductive material having adimension of length which is wound around the axis, and a dimension ofwidth which extends in the said axial direction which is no greater thanthe dimension of width of the insulation material, each of said windingscomprising at least one full turn, said windings lying between turns ofsaid insulation material, and being radially spaced fron one another byturns of the insulation material, and separated from one another alongtheir dimensions of length; and a capacitance member of flatelectrically conductive material wrapped into the spiral within arespective winding being separated therefrom by said insulation materialon both of its sides, and being electrically insulated from all othermetallic elements of the winding member. I j

43. A transformer winding member according to claim 42' inwhich terminalmeans for said windings and capacitance member comprises an end portionof the respective winding or capacitance member folded to projectlaterally beyond the winding member, the projecting portion beingmultiply folded, whereby to form a plurality of dorsal folds extendinglongitudinally along the projecting portion to form a monolithicstructure.

44. A transformer winding member according to claim 43 in which anaperture is formed continuously through the folded portion.

45. In a wound transformer winding wherein metallic foil material isutilized as a conductor, a terminal for said winding comprising an endportion of said foil material folded to project laterally beyond thetransformer winding, the projecting portion being multiply folded,whereby to form a plurality of dorsal folds extending longitudinallyalong the projecting portion to form a monolithic structure to provide aconductive connection for said conductor.

46. Structure according to claim 45 in which an aperture is formedcontinuously through the folded portion.

47. A transformer winding according to claim 4 in which a gap spacesapart the ends of the metal plate.

48. A transformer winding member according to claim 2 in which anaperture is formed continuously through the folded portion.

49. A combination according to claim 17in which an aperture is formedcontinuously through the folded portion.

50. A combination according to claim 34 in which an aperture is formedcontinuously through the folded portion.

51. A transformer winding member according to claim 42 in which acapacitance member is wrapped in each of the primary and secondarywindings.

52. A combination according to claim 19 in which a capacitance member iswrapped in each of the primary and secondary members.

53. In a wound transformer having a plurality of windings, an impedancemember respective to only one of said windings comprising a body ofmagnetizable material embracing in a radial plane at least a portion ofonly that winding.

54. Apparatus according to claim 53 in which the impedance member is ametal plate.

1. A transformer winding member having a central axis, comprising; aspirally-wound layer of flat insulation material forming a spiral andhaving a dimension of length which is wrapped around the axis, and adimension of width which extends in the said axial direction, therebeing a plurality of turns of said material; a primary winding and asecondary winding of flat electrically conductive material having adimension of length which is wound around the axis, and a dimension ofwidth which extends in the said axial direction which is no greater thanthe dimension of width of the insulation material, each of said windingscomprising at least one full turn; an electrostatic shield of flatelectrically conductive material having a dimension of length which iswound around the axis, and a dimension of width which extends in thesaid axial direction, said windings and shield lying between turns ofsaid insulation material, and being radially spaced from one another byturns of the insulation material, and separated from one another alongtheir dimensions of length, the shield lying between the windings andbeing axially aligned with at least a portion thereof.
 2. A transformerwinding member according to claim 1 in which terminal means for saidwindings and shield comprises and end portion of the material of therespective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form the said portion as a monolithic structure.3. A transformer winding member according to claim 1 in which theprimary and secondary windings and their contiguous insulation materialrespectively comprise a primary and secondary section, the insulationmaterial between these sections comprises a separation section, therebeing an impedance means of magnetizable material embracing in a radialplane at least a portion of one of the respective primary and secondarysections.
 4. A transformer winding member according to claim 3 in whichthe said impedance means comprises a metal plate.
 5. A transformerwinding member according to claim 3 in which said impedance meanscomprises a plurality of iron plates in a stack, with their endsinterleaved.
 6. A transformer winding member according to claim 1 inwhich a capacitance member of flat electrically conductive material iswrapped into the spiral within a winding, being separated therefrom bysaid insulation means on both of its sides, and being electricallyinsulated from all other metallic elements of the winding member.
 7. Atransformer winding member according to claim 6 in which a capacitancemember is wrapped into both the primary and secondary windings.
 8. Atransformer winding member according to claim 6 in which the primary andsecondary windings and their contiguous insulation material respectivelycomprise a primary and secondary section, the insulation materialbetween these sections comprises a separation section, there being animpedance means of magnetizable material embracing in a radial plane atleast a portion of one of the respective primary and secondary sections.9. A transformer winding member according to claim 8 in which the saidimpedance means comprises a metal plate.
 10. A transformer windingmember according to claim 7 in which the primary and secondary windingsand their contiguous insulation material respectively comprise a primaryand secondary section, the insulation material between these sectionscomprises a separation section, there being an impedance means ofmagnetizable material embracing in a radial plane at least a portion ofonly a respective one of the respective primary and secondary sections.11. A transformer winding member according to claim 10 in which the saidimpedance means comprises a metal plate.
 12. A transformer windingmember according to claim 10 in which said impedance means comprises aplurality of iron plates in a stack, with their ends interleaved.
 13. Atransformer winding member according to claim 6 in which terminal meansfor said windings and shield comprises and end portion of the materialof the respective winding or shield folded to project laterally beyondthe winding member, the projecting portion being multiply folded,whereby to form a plurality of dorsal folds extending longitudinallyalong the projecting portion to form a monolithic structure.
 14. Atransformer winding member according to claim 7 in which terminal meansfor said windings and shield comprises an end portion of the material ofthe respective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form a monolitic structure.
 15. A transformerwinding member according to claim 10 in which terminal means for saidwindings and shield comprises an end portion of the material of therespective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form a monolitic structure.
 16. In combination: atransformer winding member according to claim 1, and a magnetic coremember encircling the same and passing through the center thereof.
 17. Acombination according to claim 16 in which terminal means for saidwindings and shield comprises an end portion of the material of therespective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form a monolithic structure.
 18. A combinationaccording to claim 16 in which the primary and secondary windings andtheir contiguous insulation material respectively comprise a primary andsecondary section, the insulation material between these sectionscomprises a separation section, there being an impedance means ofmagnetizable material embracing in a radial plane at least a portion ofone of the respective primary and secondary sections.
 19. A combinationaccording to claim 16 in which a capacitance member of flat electricallyconductive materIal is wrapped into the spiral within a winding, beingseparated therefrom by said insulation means on both of its sides, andbeing electrically insulated from all other metallic elements of thewinding member.
 20. A combination according to claim 19 in which theprimary and secondary windings and their contiguous insulation materialrespectively comprise a primary and secondary section, the insulationmaterial between these sections comprises a separation section, therebeing an impedance means of magnetizable material embracing in a radialplane at least a portion of one of the respective primary and secondarysections.
 21. A transformer winding member according to claim 1 in whichthe electrostatic shield extends for at least one full turn, and is atleast as wide as the primary and secondary windings.
 22. A transformerwinding member according to claim 6 in which the capacitance memberextends for at least one full turn.
 23. A transformer winding memberaccording to claim 22 in which the electrostatic shield extends for atleast one full turn, and is at least as wide as the primary andsecondary windings.
 24. A transformer winding member having a centralaxis, comprising: a spirally-wound layer of flat insulation materialforming a spiral and having a dimension of length which is wrappedaround the axis, and a dimension of width which extends in the saidaxial direction, there being a plurality of turns of said material; awinding of flat electrically conductive material having a dimension oflength which is wound around the axis, and a dimension of width whichextends in the said axial direction which is no greater than thedimension of width of the insulation material, said winding comprisingat least one full turn; and electrostatic shield of flat electricallyconductive material having a dimension of length which is wound aroundthe axis, and a dimension of width which extends in the said axialdirection, said winding and shield lying between turns of saidinsulation material, and being radially spaced from one another by turnsof the insulation material, and separated fron one another along theirdimensions of length, the shield lying outside the winding and beingaxially aligned with at least a portion thereof.
 25. A transformerwinding member according to claim 24 in which the width of theelectrostatic shield is at least as great as the width of the winding.26. A transformer winding member according to claim 24 in which terminalmeans for said winding and for said shield comprises an end portion ofthe material of the respective winding or shield folded to projectlaterally beyond the winding member, the projecting portion beingmultiply folded, whereby to form a plurality of dorsal folds extendinglongitudinally along the projecting portion to form a monolilthicstructure.
 27. A transformer winding member according to claim 24 inwhich impedance means of magnetizable material embraces in a radialplane at least a portion of the winding.
 28. A transformer windingmember according to claim 27 in which the said impedance means comprisesa metal plate.
 29. A transformer winding member according to claim 27 inwhich said impedance means comprises a plurality of iron plates in astack, with their ends interleaved.
 30. A transformer winding memberaccording to claim 27 in which said impedance means comprises a metalplate whose ends are spaced apart by a gap.
 31. A transformer windingmember according to claim 24 in which a capacitance member of flatelectrically conductive material is wrapped into the spiral within thewinding, being separated therefrom by said insulation means on both ofits sides, and being electrically insulated from all other metallicelements of the winding member.
 32. A transformer winding memberaccording to claim 31 in which impedance means of magnetizable materialembraces in a radial plane at least a portion of the winding.
 33. Incombination: a pair of transformer winding members according tO claim24, and a magnetizable metallic core member extending through a centralaxial opening in both of said transformer winding members.
 34. Acombination according to claim 33 in which terminal means for saidwinding and for said shield comprises an end portion of the material ofthe respective winding or shield folded to project laterally beyond thewinding member, the projecting portion being multiply folded, whereby toform a plurality of dorsal folds extending longitudinally along theprojecting portion to form a monolithic structure.
 35. A combinationaccording to claim 33 in which impedance means of magnetizable materialembraces in a radial plane at least a portion of one of said windingsections.
 36. A combination according to claim 33 in which a capacitancemember of flat electrically conductive material is wrapped into thespiral of at least one of the winding members, and being separatedtherefrom by said insulation material on both of its sides, and beingelectrically insulated from all other metallic elements of the windingmember.
 37. A combination according to claim 36 in which impedance meansof magnetizable material embraces in a radial plane at least a portionof one of said winding sections.
 38. A transformer winding member havinga central axis, comprising: a spirally-wound layer of flat insulationmaterial forming a spiral and having a dimension of length which iswrapped around the axis, and a dimension of width which extends in thesaid axial direction, there being a plurality of turns of said material;a primary winding and a secondary winding of flat electricallyconductive material having a dimension of length which is wound aroundthe axis, and a dimension of width which extends in the said axialdirection which is no greater than the dimension of width of theinsulation material, each of said windings comprising at least one fullturn; said windings lying between turns of said insulation material, andbeing radially spaced from one another by turns of the insulationmaterial and separated from one another along their dimensions oflength; and an impedance means of magnetizable material embracing atleast a portion of only a respective one of the windings in a radialplane.
 39. A transformer winding member according to claim 38 in whichthe said impedance means comprises a metal plate.
 40. A transformerwinding member according to claim 39 in which a gap is formed betweenthe ends of the plate.
 41. A transformer winding member according toclaim 38 in which said impedance means comprises a plurality of ironplates in a stack, with their ends interleaved.
 42. A transformerwinding member having a central axis, comprising: a spirally-wound layerof flat insulation material forming a spiral and having a dimension oflength which is wrapped around the axis, and a dimension of width whichextends in the said axial direction, there being a plurality of turns ofsaid material; a primary winding and a secondary winding of flatelectrically conductive material having a dimension of length which iswound around the axis, and a dimension of width which extends in thesaid axial direction which is no greater than the dimension of width ofthe insulation material, each of said windings comprising at least onefull turn, said windings lying between turns of said insulationmaterial, and being radially spaced fron one another by turns of theinsulation material, and separated from one another along theirdimensions of length; and a capacitance member of flat electricallyconductive material wrapped into the spiral within a respective windingbeing separated therefrom by said insulation material on both of itssides, and being electrically insulated from all other metallic elementsof the winding member.
 43. A transformer winding member according toclaim 42 in which terminal means for said windings and capacitancemember comprises an end portion of the respective winding or capacitancemember folded to project laterally beyond the winding member, theprojecting portion being multiply folded, whereby to form a plurality ofdorsal folds extending longitudinally along the projecting portion toform a monolithic structure.
 44. A transformer winding member accordingto claim 43 in which an aperture is formed continuously through thefolded portion.
 45. In a wound transformer winding wherein metallic foilmaterial is utilized as a conductor, a terminal for said windingcomprising an end portion of said foil material folded to projectlaterally beyond the transformer winding, the projecting portion beingmultiply folded, whereby to form a plurality of dorsal folds extendinglongitudinally along the projecting portion to form a monolithicstructure to provide a conductive connection for said conductor. 46.Structure according to claim 45 in which an aperture is formedcontinuously through the folded portion.
 47. A transformer windingaccording to claim 4 in which a gap spaces apart the ends of the metalplate.
 48. A transformer winding member according to claim 2 in which anaperture is formed continuously through the folded portion.
 49. Acombination according to claim 17 in which an aperture is formedcontinuously through the folded portion.
 50. A combination according toclaim 34 in which an aperture is formed continuously through the foldedportion.
 51. A transformer winding member according to claim 42 in whicha capacitance member is wrapped in each of the primary and secondarywindings.
 52. A combination according to claim 19 in which a capacitancemember is wrapped in each of the primary and secondary members.
 53. In awound transformer having a plurality of windings, an impedance memberrespective to only one of said windings comprising a body ofmagnetizable material embracing in a radial plane at least a portion ofonly that winding.
 54. Apparatus according to claim 53 in which theimpedance member is a metal plate.